class Palette{
  constructor(canvasID) {
    this.canvasID = canvasID;
  }
  getPalette = ({ width, height, imgPath, colorCount, quality},cb) => {
    if (typeof colorCount === 'undefined' || colorCount < 2 || colorCount > 256) {
      colorCount = 10;
    }
    if (typeof quality === 'undefined' || quality < 1) {
      quality = 10;
    }
    let ctx = wx.createCanvasContext(this.canvasID);
    ctx.drawImage(imgPath,0,0,width,height);
    // ctx.clearRect(0,0,width,height);
    ctx.draw(false,()=>{
      wx.canvasGetImageData({
        canvasId: this.canvasID,
        x: 0,
        y: 0,
        width: width,
        height: height,
        success(res) {
          // console.log(res.width) // 100
          // console.log(res.height) // 100
          // console.log(res.data instanceof Uint8ClampedArray) // true
          // console.log(res.data.length) // 100 * 100 * 4
          var pixels = res.data;
          var pixelCount = width*height;
          var pixelArray = [];
          for (var i = 0, offset, r, g, b, a; i < pixelCount; i = i + quality) {
            offset = i * 4;
            r = pixels[offset + 0];
            g = pixels[offset + 1];
            b = pixels[offset + 2];
            a = pixels[offset + 3];
            // If pixel is mostly opaque and not white
            if (a >= 125) {
              if (!(r > 250 && g > 250 && b > 250)) {
                pixelArray.push([r, g, b]);
              }
            }
          }
          var cmap = MMCQ.quantize(pixelArray, colorCount);
          var palette = cmap ? cmap.palette() : null;
          cb(palette);
        }
      })
    })


  };
}




/*!
 * quantize.js Copyright 2008 Nick Rabinowitz.
 * Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
 * @license
 */

// fill out a couple protovis dependencies
/*!
 * Block below copied from Protovis: http://mbostock.github.com/protovis/
 * Copyright 2010 Stanford Visualization Group
 * Licensed under the BSD License: http://www.opensource.org/licenses/bsd-license.php
 * @license
 */
if (!pv) {
  var pv = {
    map: function (array, f) {
      var o = {};
      return f ? array.map(function (d, i) { o.index = i; return f.call(o, d); }) : array.slice();
    },
    naturalOrder: function (a, b) {
      return (a < b) ? -1 : ((a > b) ? 1 : 0);
    },
    sum: function (array, f) {
      var o = {};
      return array.reduce(f ? function (p, d, i) { o.index = i; return p + f.call(o, d); } : function (p, d) { return p + d; }, 0);
    },
    max: function (array, f) {
      return Math.max.apply(null, f ? pv.map(array, f) : array);
    }
  };
}



/**
 * Basic Javascript port of the MMCQ (modified median cut quantization)
 * algorithm from the Leptonica library (http://www.leptonica.com/).
 * Returns a color map you can use to map original pixels to the reduced
 * palette. Still a work in progress.
 *
 * @author Nick Rabinowitz
 * @example

// array of pixels as [R,G,B] arrays
var myPixels = [[190,197,190], [202,204,200], [207,214,210], [211,214,211], [205,207,207]
                // etc
                ];
var maxColors = 4;

var cmap = MMCQ.quantize(myPixels, maxColors);
var newPalette = cmap.palette();
var newPixels = myPixels.map(function(p) {
    return cmap.map(p);
});

 */
var MMCQ = (function () {
  // private constants
  var sigbits = 5,
    rshift = 8 - sigbits,
    maxIterations = 1000,
    fractByPopulations = 0.75;

  // get reduced-space color index for a pixel
  function getColorIndex(r, g, b) {
    return (r << (2 * sigbits)) + (g << sigbits) + b;
  }

  // Simple priority queue
  function PQueue(comparator) {
    var contents = [],
      sorted = false;

    function sort() {
      contents.sort(comparator);
      sorted = true;
    }

    return {
      push: function (o) {
        contents.push(o);
        sorted = false;
      },
      peek: function (index) {
        if (!sorted) sort();
        if (index === undefined) index = contents.length - 1;
        return contents[index];
      },
      pop: function () {
        if (!sorted) sort();
        return contents.pop();
      },
      size: function () {
        return contents.length;
      },
      map: function (f) {
        return contents.map(f);
      },
      debug: function () {
        if (!sorted) sort();
        return contents;
      }
    };
  }

  // 3d color space box
  function VBox(r1, r2, g1, g2, b1, b2, histo) {
    var vbox = this;
    vbox.r1 = r1;
    vbox.r2 = r2;
    vbox.g1 = g1;
    vbox.g2 = g2;
    vbox.b1 = b1;
    vbox.b2 = b2;
    vbox.histo = histo;
  }
  VBox.prototype = {
    volume: function (force) {
      var vbox = this;
      if (!vbox._volume || force) {
        vbox._volume = ((vbox.r2 - vbox.r1 + 1) * (vbox.g2 - vbox.g1 + 1) * (vbox.b2 - vbox.b1 + 1));
      }
      return vbox._volume;
    },
    count: function (force) {
      var vbox = this,
        histo = vbox.histo;
      if (!vbox._count_set || force) {
        var npix = 0,
          index, i, j, k;
        for (i = vbox.r1; i <= vbox.r2; i++) {
          for (j = vbox.g1; j <= vbox.g2; j++) {
            for (k = vbox.b1; k <= vbox.b2; k++) {
              index = getColorIndex(i, j, k);
              npix += (histo[index] || 0);
            }
          }
        }
        vbox._count = npix;
        vbox._count_set = true;
      }
      return vbox._count;
    },
    copy: function () {
      var vbox = this;
      return new VBox(vbox.r1, vbox.r2, vbox.g1, vbox.g2, vbox.b1, vbox.b2, vbox.histo);
    },
    avg: function (force) {
      var vbox = this,
        histo = vbox.histo;
      if (!vbox._avg || force) {
        var ntot = 0,
          mult = 1 << (8 - sigbits),
          rsum = 0,
          gsum = 0,
          bsum = 0,
          hval,
          i, j, k, histoindex;
        for (i = vbox.r1; i <= vbox.r2; i++) {
          for (j = vbox.g1; j <= vbox.g2; j++) {
            for (k = vbox.b1; k <= vbox.b2; k++) {
              histoindex = getColorIndex(i, j, k);
              hval = histo[histoindex] || 0;
              ntot += hval;
              rsum += (hval * (i + 0.5) * mult);
              gsum += (hval * (j + 0.5) * mult);
              bsum += (hval * (k + 0.5) * mult);
            }
          }
        }
        if (ntot) {
          vbox._avg = [~~(rsum / ntot), ~~(gsum / ntot), ~~(bsum / ntot)];
        } else {
          //                    console.log('empty box');
          vbox._avg = [
            ~~(mult * (vbox.r1 + vbox.r2 + 1) / 2),
            ~~(mult * (vbox.g1 + vbox.g2 + 1) / 2),
            ~~(mult * (vbox.b1 + vbox.b2 + 1) / 2)
          ];
        }
      }
      return vbox._avg;
    },
    contains: function (pixel) {
      var vbox = this,
        rval = pixel[0] >> rshift;
      gval = pixel[1] >> rshift;
      bval = pixel[2] >> rshift;
      return (rval >= vbox.r1 && rval <= vbox.r2 &&
        gval >= vbox.g1 && gval <= vbox.g2 &&
        bval >= vbox.b1 && bval <= vbox.b2);
    }
  };

  // Color map
  function CMap() {
    this.vboxes = new PQueue(function (a, b) {
      return pv.naturalOrder(
        a.vbox.count() * a.vbox.volume(),
        b.vbox.count() * b.vbox.volume()
      );
    });
  }
  CMap.prototype = {
    push: function (vbox) {
      this.vboxes.push({
        vbox: vbox,
        color: vbox.avg()
      });
    },
    palette: function () {
      return this.vboxes.map(function (vb) { return vb.color; });
    },
    size: function () {
      return this.vboxes.size();
    },
    map: function (color) {
      var vboxes = this.vboxes;
      for (var i = 0; i < vboxes.size(); i++) {
        if (vboxes.peek(i).vbox.contains(color)) {
          return vboxes.peek(i).color;
        }
      }
      return this.nearest(color);
    },
    nearest: function (color) {
      var vboxes = this.vboxes,
        d1, d2, pColor;
      for (var i = 0; i < vboxes.size(); i++) {
        d2 = Math.sqrt(
          Math.pow(color[0] - vboxes.peek(i).color[0], 2) +
          Math.pow(color[1] - vboxes.peek(i).color[1], 2) +
          Math.pow(color[2] - vboxes.peek(i).color[2], 2)
        );
        if (d2 < d1 || d1 === undefined) {
          d1 = d2;
          pColor = vboxes.peek(i).color;
        }
      }
      return pColor;
    },
    forcebw: function () {
      // XXX: won't  work yet
      var vboxes = this.vboxes;
      vboxes.sort(function (a, b) { return pv.naturalOrder(pv.sum(a.color), pv.sum(b.color)); });

      // force darkest color to black if everything < 5
      var lowest = vboxes[0].color;
      if (lowest[0] < 5 && lowest[1] < 5 && lowest[2] < 5)
        vboxes[0].color = [0, 0, 0];

      // force lightest color to white if everything > 251
      var idx = vboxes.length - 1,
        highest = vboxes[idx].color;
      if (highest[0] > 251 && highest[1] > 251 && highest[2] > 251)
        vboxes[idx].color = [255, 255, 255];
    }
  };

  // histo (1-d array, giving the number of pixels in
  // each quantized region of color space), or null on error
  function getHisto(pixels) {
    var histosize = 1 << (3 * sigbits),
      histo = new Array(histosize),
      index, rval, gval, bval;
    pixels.forEach(function (pixel) {
      rval = pixel[0] >> rshift;
      gval = pixel[1] >> rshift;
      bval = pixel[2] >> rshift;
      index = getColorIndex(rval, gval, bval);
      histo[index] = (histo[index] || 0) + 1;
    });
    return histo;
  }

  function vboxFromPixels(pixels, histo) {
    var rmin = 1000000, rmax = 0,
      gmin = 1000000, gmax = 0,
      bmin = 1000000, bmax = 0,
      rval, gval, bval;
    // find min/max
    pixels.forEach(function (pixel) {
      rval = pixel[0] >> rshift;
      gval = pixel[1] >> rshift;
      bval = pixel[2] >> rshift;
      if (rval < rmin) rmin = rval;
      else if (rval > rmax) rmax = rval;
      if (gval < gmin) gmin = gval;
      else if (gval > gmax) gmax = gval;
      if (bval < bmin) bmin = bval;
      else if (bval > bmax) bmax = bval;
    });
    return new VBox(rmin, rmax, gmin, gmax, bmin, bmax, histo);
  }

  function medianCutApply(histo, vbox) {
    if (!vbox.count()) return;

    var rw = vbox.r2 - vbox.r1 + 1,
      gw = vbox.g2 - vbox.g1 + 1,
      bw = vbox.b2 - vbox.b1 + 1,
      maxw = pv.max([rw, gw, bw]);
    // only one pixel, no split
    if (vbox.count() == 1) {
      return [vbox.copy()];
    }
    /* Find the partial sum arrays along the selected axis. */
    var total = 0,
      partialsum = [],
      lookaheadsum = [],
      i, j, k, sum, index;
    if (maxw == rw) {
      for (i = vbox.r1; i <= vbox.r2; i++) {
        sum = 0;
        for (j = vbox.g1; j <= vbox.g2; j++) {
          for (k = vbox.b1; k <= vbox.b2; k++) {
            index = getColorIndex(i, j, k);
            sum += (histo[index] || 0);
          }
        }
        total += sum;
        partialsum[i] = total;
      }
    }
    else if (maxw == gw) {
      for (i = vbox.g1; i <= vbox.g2; i++) {
        sum = 0;
        for (j = vbox.r1; j <= vbox.r2; j++) {
          for (k = vbox.b1; k <= vbox.b2; k++) {
            index = getColorIndex(j, i, k);
            sum += (histo[index] || 0);
          }
        }
        total += sum;
        partialsum[i] = total;
      }
    }
    else {  /* maxw == bw */
      for (i = vbox.b1; i <= vbox.b2; i++) {
        sum = 0;
        for (j = vbox.r1; j <= vbox.r2; j++) {
          for (k = vbox.g1; k <= vbox.g2; k++) {
            index = getColorIndex(j, k, i);
            sum += (histo[index] || 0);
          }
        }
        total += sum;
        partialsum[i] = total;
      }
    }
    partialsum.forEach(function (d, i) {
      lookaheadsum[i] = total - d;
    });
    function doCut(color) {
      var dim1 = color + '1',
        dim2 = color + '2',
        left, right, vbox1, vbox2, d2, count2 = 0;
      for (i = vbox[dim1]; i <= vbox[dim2]; i++) {
        if (partialsum[i] > total / 2) {
          vbox1 = vbox.copy();
          vbox2 = vbox.copy();
          left = i - vbox[dim1];
          right = vbox[dim2] - i;
          if (left <= right)
            d2 = Math.min(vbox[dim2] - 1, ~~(i + right / 2));
          else d2 = Math.max(vbox[dim1], ~~(i - 1 - left / 2));
          // avoid 0-count boxes
          while (!partialsum[d2]) d2++;
          count2 = lookaheadsum[d2];
          while (!count2 && partialsum[d2 - 1]) count2 = lookaheadsum[--d2];
          // set dimensions
          vbox1[dim2] = d2;
          vbox2[dim1] = vbox1[dim2] + 1;
          //                    console.log('vbox counts:', vbox.count(), vbox1.count(), vbox2.count());
          return [vbox1, vbox2];
        }
      }

    }
    // determine the cut planes
    return maxw == rw ? doCut('r') :
      maxw == gw ? doCut('g') :
        doCut('b');
  }

  function quantize(pixels, maxcolors) {
    // short-circuit
    if (!pixels.length || maxcolors < 2 || maxcolors > 256) {
      //            console.log('wrong number of maxcolors');
      return false;
    }

    // XXX: check color content and convert to grayscale if insufficient

    var histo = getHisto(pixels),
      histosize = 1 << (3 * sigbits);

    // check that we aren't below maxcolors already
    var nColors = 0;
    histo.forEach(function () { nColors++; });
    if (nColors <= maxcolors) {
      // XXX: generate the new colors from the histo and return
    }

    // get the beginning vbox from the colors
    var vbox = vboxFromPixels(pixels, histo),
      pq = new PQueue(function (a, b) { return pv.naturalOrder(a.count(), b.count()); });
    pq.push(vbox);

    // inner function to do the iteration
    function iter(lh, target) {
      var ncolors = 1,
        niters = 0,
        vbox;
      while (niters < maxIterations) {
        vbox = lh.pop();
        if (!vbox.count()) { /* just put it back */
          lh.push(vbox);
          niters++;
          continue;
        }
        // do the cut
        var vboxes = medianCutApply(histo, vbox),
          vbox1 = vboxes[0],
          vbox2 = vboxes[1];

        if (!vbox1) {
          //                    console.log("vbox1 not defined; shouldn't happen!");
          return;
        }
        lh.push(vbox1);
        if (vbox2) {  /* vbox2 can be null */
          lh.push(vbox2);
          ncolors++;
        }
        if (ncolors >= target) return;
        if (niters++ > maxIterations) {
          //                    console.log("infinite loop; perhaps too few pixels!");
          return;
        }
      }
    }

    // first set of colors, sorted by population
    iter(pq, fractByPopulations * maxcolors);

    // Re-sort by the product of pixel occupancy times the size in color space.
    var pq2 = new PQueue(function (a, b) {
      return pv.naturalOrder(a.count() * a.volume(), b.count() * b.volume());
    });
    while (pq.size()) {
      pq2.push(pq.pop());
    }

    // next set - generate the median cuts using the (npix * vol) sorting.
    iter(pq2, maxcolors - pq2.size());

    // calculate the actual colors
    var cmap = new CMap();
    while (pq2.size()) {
      cmap.push(pq2.pop());
    }

    return cmap;
  }

  return {
    quantize: quantize
  };
})();

export default Palette;